Hydraulic die cushion



Oct. 19 1925. 1,603,398

0. 3. NlLSON HYDRAULIC DIE CUSHION Filed March 9. 1925 Patented Get. 19, 1926.

UNETED STATES ,OLOF G. NILSON, OE CHICAGO, ILLINOIS.

HYDRAULIC DIE CUSHION.

Application filed March 9, 1925. Serial No. 14,135.

My invention relates to die cushions for punch presses, or to means for yieldingly gripping the edges of a blank to be formed under a die to prevent the metal from wrinkling under the process. The object of the present invention is to provide an irnprovement upon both pneumatic and spring types of cushions, to the ends of a larger range of capacity for a given size of mechanism, a safer and more economical mode of operation, and to avoid the danger of explosion which attends the use of air, steam, or other gas as a force. The invention further consists in such other related advantages and improvement in mechanism as will appear from the subjoined descrip tion. And the invention consists in the novel construction, combination and arrange ment of parts, all as hereinafter described in detail, illustrated in the accompanying drawing and more particularly pointed out in the appended claims.

In the drawing Figure 1 is a vertical section through a die-cushion mechanism embodying my invention;

Fig. 2 is a section taken substantially on the line 22 of Fig. 1; and

Fig. 3 is a modification of the Fig. 2 construction in which the stuffing-box oi Fig 2 is eliminated.

In the several views 2 and 3 represent, respectively, a storage cylinder and superposed frame to hold oil or liquid under pres sure, and a die-cushion pressure cylinder.

The cylinders 2 and 3 are placed in communication with each other through a pipe 4 as a conduit for oil or liquid under pressure from the bottom of the cylinder 2, which enters a valve-chamber in the bottom of the cylinder 8.

Referring, first, to the mechanism of the storage cylinder 2, the latter is provided with a piston 6 beneath which oil or liquid is poured into a space 7. In the latter the liquid is compressed under a yielding pres sure under a coiled spring 8, the upper end of which bears against a cap or head 9 with a central boss 10 which enters the coil of the spring 8. The head 9-10 is moved against the spring, the lower end of which rests on the piston 6, by means of a screw 11 which has keyed to it hand-wheel 12 and operates in a nut 13 secured in a crossbar 14 supported by vertical standards 14, 14 that rise from opposite sides of the cylinder Through the piston 6 is a central and vertical bore 15 which is occupied by a tubular and valve-controlled member 16, which provides a relief-port 17 between the compression space 7 below the piston and the atmosphere above it. The port 17 1s controlled by a valve 18 which seats against a lower end, or offset, of the tube 16 which is provided with an annular flange 19, or shoulder. From the enlarged periphery of the latter depends a socket-member 20-, which may be a counterbored extension of the tube 16. The socket-member is slidable on a post 21 that is secured to the bottom-22of the cylinder 2. In the upper end of the socket-member 20 are lateral ports .13, 23 through which liquid from below the piston 6 may flow through the passage 17 when the valve 18 is moved downward, or opened. Said valve has a stem 24 the upper end of which is threaded as at 25 and engaged with a nut 26 which bears against the upper end of a small coiled spring 26, the lower of which rests on an annular shoulder 27 formed by a counterbored portion of the tube 16.

As shown, the tube 16 projects above the piston 6 and has its upper end threaded and in engagement with a nut 28 by means of which a shoulder 29 formed by the flange 19, is drawn fluid-tight against the bottom of the piston 6. A pin 29 is secured in the head 9, 10 and is arranged to contact with the stem 24 of the valve 18 to cause the latter to act as a safety-valve to relieve undue pressure in the chamber 7, the space be tween the threaded upper end of the stem 24 and the pin 29' representing the maximum movement against or compressionot the spring 8 on the down stroke of the press, or the hereinafter referred to piston in the cylinder 8.

The function of the stud 21 and socket 20 is to prevent a tipping of binding move ment of the piston 6 against the sides of the cylinder 2. Said piston is provided with an annular packing in the form of an in verted U in cross section, shown at 30. The interior of this U or channel packing 30 is open to the pressure-chamber 7 so that the pressure from the latter will expand the packing against the sides of the cylinder, through suitable openings 31, 31 that pass through a metal ring 32 secured by screws 33.

Through the piston 6 is also another Ill) opening 34 normally closed by a plug 35 which has threaded engagement with said opening. This is an inlet opening through which oil or liquid is poured into the cham her 7. Below the piston 6 and resting on the bottom 22 is a coiled expansion spring 36 which yieldingly supports the piston (3 against dropping to said bottom, This spring surrounds the socket 20.

The left hand end of the pipe a enters the bottom of the valvethamber o. The latter extends from the bottom3T-of the diecushion cyl nder Vithin the valve-chain ber 5 is formed a chamber 88 mostly of annular form by means of an inner cylinder 39 which open to the interior of the cylinder 3 and is spaced apart from the inner walls and bottom of the chamber 5, as shown. The inner cylinder 39 also depends from the bottom 37 and has in its bottom an inlet opening 40 that is controlled by a flat poppet valve 41 of smaller diameter than the space within the cylinder 39. On the valve a1 is an upwardly extending stem l2 to which is secured wings 43, ii, and 4% on its upper end and sim lar wings 43, it-l, 45 and d6 on its lower end. These wings are, as shown in Figure 2, arranged to form crosses which span the spaces between the stem and the sides of the cylinder 39 and serve to support the valve il against tipping or angular movement. In one side of the inner cylinder 39 is a port 4.7 that is controlled by a valve 18 that is placed in the annular space 38 and is provided with a stud 49 which en ters one end of a coiled spring 50 within a thamber 51 in a cylindrical lateral projection 52 the outer end of wh ch is closed. The part 52 has a reduced and threaded portion 53 which is engaged with a correspondingly threaded bore 5 1 in the side of the valvechamber 5 and is concentric with the port it. Slidable within the chamber 51 is a nut 55 with wh ch a screw 56 has threaded engagement. The nut 55 is held against rotary movement with its screw 56 by a lug 57 on said nut, which lug moves in a slot 58 formed in the upper side of the Chamber 51 by a horizontal bore through the closed end of the chamber and in the side thereof. This bore is closed at ts outer end59-by a plug 60. A reduced shank portion 61 of the screw is journaled in said end 59 in a bore 62 and is provided with a turning knob 63 by means of which the screw is manually rotated. The shank portion 61 thereof is made fluid t ght by a stuiiing-box 64 in Figure 1 and by a disk 65 which is shrunk on or keyed to the stem or shank 61 in the Figure 8 construction. The spring 50, or a similar spring 50 in Figure 3, is tensioned by movement of the nut 55 in Figure 1, or a corresponding nut 55 in Figure 3 which is provided with a hub portion, as shown, which enters the spring 50, against the valve 48 (Fig. 1). In Figare 3 this valve is in the form of a short cylinder 3 with one end closed, which receives the one end of the spring 50. In Figure 1 the same end of the spring is engaged interiorly by the stud 49. In Figure the nut is movable within a hollow plug 65 which has threaded engagement with a chamber 51 that serves the same purpose as the chamber 51 in Figure 1, and is formed in a thickened portion of a wall of the valve chamber 5. In connection with the storage cylinder 2, G6, 66 are lugs or flanges on the cylinder 2 which are clamped to similar lugs 67 on the uprights 14, 14 by means of screws 68.

The die-cushion cylinder 3 is provided with a piston (59 which is like the piston 6 without the openings through the latter. To the piston 69 is secured a suitable number of rods or legs 70 and 71 wh ch are slidable hrough bores 72 and T3 in the top7l-of the cylinder 3. These rods support on their upper ends a ring 75 from which rise a suitable number of the draw-ring supporting rods-7ti and 77 which are slidable through bores made therefor in the die-shoe 78 carried on a suitably supported bolster in the usual manner. The bolster-79-has a large opening 79 therethrough for said rods 76 and 77 and for a cylinder-supporting post 80 which has threaded engagement with the dicshoe 79 and top 7% of the cylinder, as shown at 81 and 82.

In Figure 1 the piston (59 is shown in its lowered position as at the end of drawing or die-forming operation when the downwardly moving die has forced down the draw-ring rods 76 and '77. Said movement has forced up the piston (3 in the cylinder 2 to the raised position in which it is shown, the fluid returning from the cylinder 3 toward the chamber '7 by way of the bypass i7, the alve 18 for same having been opened by the pressure against it, and the conduits 58 and 4:. This return movement of the "fluid is also resisted by the spring 50 pressure aga nst the valve 48, which latter resistance will be suitably varied or adjusted by operation of the screw 56 in the nut 55 which bears against the right hand end of said spring 50. The downward pressure of tlre die against the rods 76 and 77 being relieved on the upward stroke of the press tire pressure of the l quid under the spring 5 will raise the piston and release the formed shell, or the work, in the usual and well known manner.

The advantages of the above described construction is that the pressure in the chamber 7 may be accurately regulated not to exceed the force required to lift the shaped or drawn shell out of the die, while with other forces, such as steam and air, heretofore used, special provision and mechanism is required to prevent, or lock, the upward movement of the cushion of the cylinder 3, or its substitute, against the quick upthrow and a damaging and annoying noise of a clutch slam. This for the reason that with my improved mechanism if, say, twenty thousand pounds resistance is necessary to properly draw a given size or thickness of shell or work it is not necessary to have more than, say, one hundred pounds pressure in the chamber 7, or whatever force is necessary to lift the mechanism superposed on the piston 69 and lift the shell or work out of the die. In other words, the grip upon the work between the die and drawring is regulated by the pressure of the spring against the opening movement of the valve 418, while the force necessary to lift the die and release the formed work or shell, being always substantially the same for a given character of operations, is ad justed by the screw 11 and the pressure of the spring 8.

The storage cylinder 2 being made of proper dimensions, is adapted to be connected with, or serve, more than one cushion or diepress. This hydraul c mechanism eliminates the danger of explosion incidental to more expanding forces, the expensive and con'iplicated mechanism for creating which is, in the present invention supplant ed by the simple and harmless springs 8 and 50. The steam or pneumatic forces also require comparatively large cylinders or pressure-chembers, and then cannot be safely operated under pressure exceeeding one hundred pounds. \Vith the present improvement, on the other hand, there is no limit, other than the strength of the walls of the hydraulic pressure-chamber or cylinder, to the amount of pressure that may be safely used. Then, too, air-compressors easily become deranged, require frequent repairs, and an extra compressor must be provided or the die-cushion must remain idle while its compressor is being repaired.

I claim as my invention 1. A die-cushion-operating mechanism comprising a chamber 7 having a piston therein under variable pressure and adapted to contain a liquid under such pressure, and a cushionpiston-cylinder in communication with said chamber 7 through a valvecontrolled conduit, a valve closing said con-- duit against movement in one direction of liquid passing therethrough, a bypass for return of liquid in said one direction, a valve normally closing said passage, and variably yielding means for holding said by-pass valve closed.

2. The combination with a fluid-storage cylinder and a piston therein. of a die-cushion cylinder and a piston in the latter, of variable pressure-means for holding the storage cylinder piston under pressure against the liquid in said cylinder, a conduit connecting the two cylinders, a valve controlling the flow of liquid passing through said conduit in one direction, a by-pass and a valve therefor controlling the flow of said liquid in the opposite direction, and variable resistance means for resisting the flow from said die-cushion cylinder.

3. The combination with a fluid storage cylinder, of a piston therein and a fluid-pressure chamber on one side of said piston, yielding compression means operating against the opposite side of said piston, means for varying the strength of said compression means, a valve-controlled conduit through said piston, automatically-operating means for opening said valve to permit liquid to How from said fluid-pressure chamber, a normally closed fluid-inlet into said fluid-pressure chamber, a die-cushion cylinder, a conduit leading into the latter from said storage chamber, a vavle automatically closing said conduit against a return flow of liquid into said storage chamber, a by-pass connecting the interior of said die-cushion cylinder with the conduit between said storage and die-cushion cylinders, a yieldingly seated valve normally closing said bypass and resisting movement of liquid therethrough, variable resistance means operating against the latter valve, a piston in said die-cushion cylinder operable by fluid under pressure flowing into said die-cushion cylinder and means supported on the latter piston and extending out of said die-cushion cylinder for supporting a draw-ring.

l. The combination with movable supports for draw ring, of a piston carrying said supports, hydraulic means for moving said piston in one direction and variable resistance means permitting said piston to move in the opposite direction.

In testimony whereof I have hereunto signed my name.

oLoF e. NILSON. 

